Optical communication system, optical transmitter, and transponder
First Claim
Patent Images
1. An optical communication system comprising:
- an optical transmitter that maps digital data to a plurality of subcarriers which are orthogonal to each other over symbol time so as to be modulated and transmitted as an optical signal via an optical fiber; and
an optical receiver that performs photoelectric conversion on the optical signal which has propagated through the optical fiber and demodulates each subcarrier signal so as to reproduce original digital data, whereinthe optical transmitter includesa transmission signal processing unit that maps digital data to a plurality of subcarriers orthogonal to each other over symbol time so as to be modulated, and generates a base band OFDM signal from the modulated subcarrier signal; and
an electric-optic conversion unit that modulates the base band OFDM signal into laser light so as to generate an optical OFDM signal,the transmission signal processing unit and the electric-optic conversion unit transmit optical OFDM signals with alternately different wavelengths for each symbol time, andthe optical receiver includesat least one set of a delay interferometer that delays a portion of the optical OFDM signal received from the optical transmitter via the optical fiber by the symbol time so as to be combined with the optical OFDM signal and a balanced photoelectric conversion unit that converts the combined optical signal into an electric signal; and
a reception signal processing unit that obtains a subcarrier signal from an output of the photoelectric conversion unit and demodulates data from the subcarrier signal so as to reproduce original digital data.
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Abstract
A technique for reducing a necessary bandwidth of an optical receiver in an optical OFDM communication system is disclosed. Optical OFDM signals of different spectra are alternately transmitted for each OFDM symbol time, and; after this light is transmitted via an optical fiber, the light undergoes photoelectric conversion by a delay interferometer having a delay time equal to one symbol time and a balanced direct detection receiver and is received.
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Citations
12 Claims
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1. An optical communication system comprising:
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an optical transmitter that maps digital data to a plurality of subcarriers which are orthogonal to each other over symbol time so as to be modulated and transmitted as an optical signal via an optical fiber; and an optical receiver that performs photoelectric conversion on the optical signal which has propagated through the optical fiber and demodulates each subcarrier signal so as to reproduce original digital data, wherein the optical transmitter includes a transmission signal processing unit that maps digital data to a plurality of subcarriers orthogonal to each other over symbol time so as to be modulated, and generates a base band OFDM signal from the modulated subcarrier signal; and an electric-optic conversion unit that modulates the base band OFDM signal into laser light so as to generate an optical OFDM signal, the transmission signal processing unit and the electric-optic conversion unit transmit optical OFDM signals with alternately different wavelengths for each symbol time, and the optical receiver includes at least one set of a delay interferometer that delays a portion of the optical OFDM signal received from the optical transmitter via the optical fiber by the symbol time so as to be combined with the optical OFDM signal and a balanced photoelectric conversion unit that converts the combined optical signal into an electric signal; and a reception signal processing unit that obtains a subcarrier signal from an output of the photoelectric conversion unit and demodulates data from the subcarrier signal so as to reproduce original digital data. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10)
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11. An optical transmitter in an optical communication system comprising the optical transmitter that maps digital data to a plurality of subcarriers which are orthogonal to each other over symbol time so as to be modulated and transmitted as an optical signal via an optical fiber and an optical receiver that delays by the symbol time a portion of the optical signal which has propagated through the optical fiber so as to be combined with the optical signal, performs photoelectric conversion on the combined optical signal, and demodulates each subcarrier signal so as to reproduce original digital data,
the optical transmitter comprising: -
a transmission signal processing unit that maps digital data to a plurality of subcarriers orthogonal to each other over symbol time so as to be modulated, and generates a base band OFDM signal from the modulated subcarrier signal; and an electric-optic conversion unit that modulates the base band OFDM signal into laser light so as to generate an optical OFDM signal, wherein the transmission signal processing unit and the electric-optic conversion unit transmit optical OFDM signals with alternately different two wavelengths for each symbol time.
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12. A transponder in an optical communication system comprising:
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an optical transmitter that maps digital data to a plurality of subcarriers which are orthogonal to each other over symbol time so as to be modulated and transmitted as an optical signal via an optical fiber; and an optical receiver that performs photoelectric conversion on the optical signal which has propagated through the optical fiber and demodulates each subcarrier signal so as to reproduce original digital data, the transponder comprising the optical transmitter and the optical receiver, wherein the optical transmitter includes a transmission signal processing unit that maps digital data to a plurality of subcarriers orthogonal to each other over symbol time so as to be modulated, and generates a base band OFDM signal from the modulated subcarrier signal; and an electric-optic conversion unit that modulates the base band OFDM signal into laser light so as to generate an optical OFDM signal, wherein the transmission signal processing unit and the electric-optic conversion unit transmit optical OFDM signals with alternately different two wavelengths for each symbol time, and the optical receiver includes at least one set of a delay interferometer that delays a portion of the optical OFDM signal received from the optical transmitter via the optical fiber by the symbol time so as to be combined with the optical OFDM signal and a balanced photoelectric conversion unit that converts the combined optical signal into an electric signal; and a reception signal processing unit that obtains a subcarrier signal from an output of the photoelectric conversion unit and demodulates data from the subcarrier signal so as to reproduce original digital data.
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Specification